Snap-action electrical switch with contact dampening means



March 9, 1965 H. E. SCHLEICHER SNAP-ACTION ELECTRICAL SWITCH WITHCONTACT DAMPENING MEANS Filed May 2, 1963 mm T.C N E mm BY MS al/omeysUnited States Patent 3,172,972 SNAP-ACTION ELECTRECAL SWITCH-i WiTHCONTACT DAMPENlNG MEANS Harold E. Schleicher, West Hartford, Conn.,assignor to The Arrow-Hart 3; Hegeman Electric Company, Hartford, Conn,a corporation of Connecticut Filed May 2, 1963, Ser. No. 277,624 4-Claims. (Ql. 20067) This invention relates to lever-operated electricswitches. More particularly, it relates to means to quiet the action oflever-operated electric switches.

Heretofore, switches have been designed to operate quietly without theusual loud click heard in the many old style lever-operated electricswitches of the over-center spring action type. One example of suchquiet action switch is found in Bentley Patent 2,725,438.

While the switch of the Bentley type provided a positive action and feelas the switch was operated and was quiet in operation as compared to oldstyle over-center manually operated switches, they, nevertheless, didhave a perceptable click on operation from one position to another whichcan be heard in silent rooms or rooms Where there is a low level ofnoise. This click tends to increase as the switch grows older,particularly when the switch was mounted behind a wall plate of hardmolded insulating material, such as are now in general use. The platesact like a sounding board to amplify the sound of the click incident tothe operation of the switch.

In quiet action switches of the type disclosed in the above-mentionedBentley patent of either the single-throw or double-throw type, therewas a tendency of the movable contact to chatter or rebound whenengaging the fixed contact due to the inherent springiness of thefiexible movable contact arm in connection with the over-center spring.This was even more pronounced when rubber bumpers were used as stops forthe operating lever.

The overenter spring is a necessary and desired element because (a) ofthe desire of the user to feel a positive change from one position toanother, and (b) of the need to hold the manual operating lever in itstwo opposite positions after it has been moved from one position to theother.

Thus, an object of the invention is to reduce to a nummum or practicallyinaudible level the noise incident to operation of lever-operatedelectric switches of the overcenter spring type and particularly of thetype which are designed for normally quieter action.

Another object is to provide means to quiet the action of lever-operatedelectric switches of the over-center spring type and to dampen theaction of the same so as to overcome the tendency to chatter or reboundas the switch lever stops in moving to its opposite positions and as themovable contact comes into engagement with the fixed contacts, thus toprolong the life of the switch contacts and reduce the noise incident toswitch operation.

Other objects and advantages of the invention will appear as it isdescribed in connection with the accompanying drawing.

In the drawing:

FIG. 1 is a longitudinal elevational section view of a switch embodyingthe invention with the section taken along line 1-1 of FIG. 2.

FIG. 2 is a plan view of a switch embodying the invention with the topor cover of the switch housing removed.

FIG. 3 is a detail view of the handle used in the switch of FIG. 1.

Referring to the drawing, the operating parts of the switch are housedwithin a hollow casing made preferably of molded insulation materialwith a cup-shaped base section open at the top and a cover 12 fittingwithin the casing walls at the top edges thereof in usual fashion. At

3,172,972 Patented Mar. 9, 1965 opposite ends of the casing, metalterminal plates 16 and 18 are mounted in conventional fashion, as bysliding inwardl into slots at the ends of the casing. Attached to theplate 16 is the short leg of an L-shaped movable contact member 17having a contact button of silver or other good highly conductivecontact material on its opposite or free end.

The movable contact member 17 is preferably a thin strip of flexibleresilient electrically conductive metal bent into L-shape.

The movable contact button 17c may engage and disengage a fixed contactbutton of similar material to the movable contact button, but mounted onthe upper surface of an in-turned upper end of the terminalplate 18.

The movable contact member 17 is biased by inherent springiness orresilience to a closed position in which the button 170 engages thebutton 180.

To move the movable contact member 17, a switch operating lever 2t) ofmolded insulating material has trunnions 22 thereon by which the leveris pivotally mounted in seats 19 in the upper edge of the base 10'. Tooperate the movable contact member, a cam finger or extension 24 extendsinwardly into the base it to press the movable contact member down andcause it to disengage the fixed contact in the position shown in FIG. 1.There may be two such fingers adjacent opposite trunnions 22, if theinvention is applied to a switch having two movable contact members on oposite sides of the casing, such as a twopole, a three or four-wayswitch.

When the switch is in the position shown in FIG. 1, the cam finger 24presses down the movable contact member 17 and holds the contact button170 from engaging the fixed contact button 186.

On moving the lever 20 clockwise from the position of FIG. 1, the camfinger 24 will rotate clockwise and allow the movable contact member 17to move its button 17c into engagement with the fixed contact button18c.

To hold the lever 17 either in on position or in its opposite offposition, an over-center coiled compression spring 28 has one end seatedon a spring-holding stud 29 molded in the bottom of the base 10 whileits other end engages a spring-operating finger 26 molded on the lever2t} and extending centrally thereof between the movable contactoperating cams 24.

In order to reduce the noise of operation of the lever from one positionto the other, rubber bumpers 25 may be provided within the casing atopposite ends to act as stops for the shoulders 23 formed on the leverZil. These shoulders lie on opposite sides of the pivotal axis of thelever; and upon abutting the bumpers, the bumpers absorb the sound ofthe lever coming to rest in its opposite positions. However, the bumpersare resilient and, hence, tend to rebound. Since the movable contact arm17, when in direct engagement with the cam 24 in previous switchestended to follow every movement of the cam, there was a pronouncedtendency of the switch parts to rebound when the rubber bumpers wereused. This caused noise, but at a lower lever than when the levershoulders struck solid stops on the casing.

Bumpers 25 may be elongated rectangular pieces of rubber or otherelastic material which may be slid downwardly into the open top pocketsor recesses P which extend up centrally at the top end of the base 1%from the floor thereof. The bumpers may have heads overlying the topedges of the pockets P.

For the fourfold purpose of (a) dampening vibrations of the movablecontact member 17 as its button strikes the fixed contact button 180 and(b) mufiiing the sound of the switch action and (c) quieting the actionof the movable contact button as it engages the fixed contact button and(d) quieting the action of the lever 29 as it stops in one position orthe other, a felt pad or membrane 30 is provided and placed between themovable contact member 17 and the lever 20.

The membrane is rectangular in shape like the interior outline of thebase cavity and of approximately the same size and contour so as to fitwithin the base at its top. The membrane 30 has a central aperture 32through which the spring-operating finger 26 extends to engage the upperend of the spring 28. The membrane lies between the other parts of theinner end of the lever 20 and all interior parts of the switchmechanism.

Four circular button-like nubs 12a extend inwardly from the underside ofthe cover 12 at the four corners of the cover at four positions over thefixed contact and the anchored end of the movable contact member. Whenthere are pairs of fixed and movable contacts on each side of thecasing, these nubs press on the membrane clamping it at four pointsbetween the cover and contacts.

As the lever 20 is moved from the position shown in FIG. 1 to theopposite position and back, the contact operating cam 24 slides over thefelt membrane with minimum friction because the lever is made of smoothsurfaced molded plastic material and slides easily over the feltmembrane.

When there is only one pair of fixed and movable contacts, the nubs 12aat opposite ends of the cover press on the membrane at opposite endsholding it on that side when the cam 24 acts on the movable contactmember. When there is no movable contact on the opposite side, there isno stress on the membrane by the cam 24 on that side.

Another advantage of the membrane is that the fiber gasket whichconventionally was used between the mounting plate or bridge 14 and thecover 12 to keep dust out of the casing and are flashes from themounting plate or bridge is no longer necessary, as the felt membraneperforms those functions too. It has been found the felt has lesstendency to burn than the fibre.

Thus, the felt membrane performs the above-mentioned rebound, dampening,noise-reducing, noise-muffiing and arc-quenching functions, considerablyimproving the operation of the switch over those heretofore known.

Any material can be used for the membrane which possesses the propertiesof absorption of sound, absorption and dampening of inertial force andhigh resistance to burning by an electric arc, and is tough and wearresistant under the continuous rubbing and friction of the operatinglever. Although the operating lever and its end 25 are molded andsmooth, the end must be pointed to give the usual and desiredover-center action in combintion with the over-center spring 28 andtoggle point 26. Woven wool felt is preferred, but pressed wool is alsosatisfactory and has proved sufficiently wear-resistant under testconditions. These are preferred over cotton which chars and burns morereadily.

Many modifications within the scope of the invention will occur to thoseskilled in the art. Therefore, the invention is not limited to thespecific form and configuration illustrated.

What is claimed is:

1. In an electric switch, a hollow casing housing the switch parts, amovable contact, another contact engageable and disengageable by saidmovable contact as the latter moves between two at-rest positions, aresilient arm on which said movable contact is mounted biasing saidmovable contact toward engagement with said other contact, amovable-contact-operating lever having a cam surface thereon forseparating said movable contact from said other contact, spring meansacting on said lever to bias it in two at-rest positions, said movablecontact and resilient arm tending to chatter when moved into engagementwith said other contact, a flexible member extending entirely acrosssaid casing and from end to end and having an aperture therethrough forsaid lever to engage said spring means, said flexible member beinglocated between said cam surface and said resilient contact-carryingarm, said flexible member being formed of a damping material which ishighly resistant to burning by contact arcing, and being of sufficientthicknes to overcome the tendency of said movable contact and arm tochatter, said damping member also deadening the sound of switch openingand closing movement.

2. An electric switch as claimed in claim 1 having stops at oppositeends of the casing for said switch lever which tend to make said leverand movable contacts rebound, said flexible member extending betweensaid stops and said lever absorbing the inertia of the switch parts andwhile simultaneously performing said dampening and noise deadeningactions.

3. An electric switch as claimed in claim 2 in which said flexiblemember is a felt pad.

4. An electric switch as claimed in claim 1 in which said flexiblemember is a felt pad.

References Cited by the Examiner UNITED STATES PATENTS 2,457,153 12/48Hubbell 20067 2,725,438 11/55 Bentley 200-67 FOREIGN PATENTS 690,5904/40 Germany.

BERNARD A. GILHEANY, Primary Examiner.

ROBERT K. SCI-IAEFER, Examiner.

1. IN AN ELECTRIC SWITCH, A HOLLOW CASING HOUSING THE SWITCH PARTS, AMOVABLE CONTACT, ANOTHER CONTACT ENGAGEABLE AND DISENGAGEABLE BY SAIDMOVABLE CONTACT AS THE LATTER MOVES BETWEEN TWO AT-REST POSITIONS, ARESILIENT ARM ON WHICH SAID MOVABLE CONTACT IS MOUNTED BIASING SAIDMOVABLE CONTACT TOWARD ENGAGEMENT WITH SAID OTHER CONTACT, AMOVABLE-CONTACT-OPERATING LEVER HAVING A CAM SURFACE THEREON FORSEPARATING SAID MOVABLE CONTACT FROM SAID OTHER CONTACT, SPRING MEANSACTING ON SAID LEVER TO BIAS IT IN TWO AT-REST POSITIONS, SAID MOVABLECONTACT AND RESILIENT ARM LEADING TENDING TO CHATTER WHEN MOVED INTOENGAGEMENT WITH SAID OTHER CONTACT, A FLEXIBLE MEMBER EXTENDING ENTIRELYACROSS SAID CASING AND FROM END TO END AND HAVING AN APERTURETHERETHROUGH FOR SAID LEVER TO ENGAGE SAID SPRING MEANS, SAID FLEXLIBLEMEMBER BEING LOCATED BETWEEN SAID CAM SURFACE AND SAID RESILIENTCONTACT-CARRYING ARM, SAID FLEXIBLE MEMBER BEING FORMED OF A DAMPINGMATERIAL WHICH IS HIGHLY RESISTANT TO BURNING BY CONTACT ARCING, ANDBEING OF SUFFICIENT THICKNES TO OVERCOME THE TENDENCY OF SAID MOVABLECONTACT AND ARM TO CHATTER, SAID DAMPING MEMBER ALSO DEADENING THE SOUNDOF SWITCH OPENING AND CLOSING MOVEMENT.